1. Field of Invention
This invention relates to fuser and fixing members. More particularly, this invention related to such fuser and fixing members that include a PEI-b-PDMS (polyetherimide-block-polysiloxane, such as PDMS) block copolymer as a surface layer thereon.
2. Description of Related Art
In a typical electrostatographic printing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles, which are commonly referred to as toner. The visible toner image is then in a loose-powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be a photosensitive member itself or other support sheet such as plain paper, transparency, specialty coated paper, or the like.
The use of thermal energy for fixing toner images onto a support member is well known. In order to fuse electroscopic toner material onto a support surface permanently by heat, it is necessary to-elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90° C. to about 160° C. or higher, depending upon the softening range of the particular resin used in the toner. It is not desirable, however, to raise the temperature of the substrate substantially higher than about 200° C. because of the tendency of the substrate to discolor at such elevated temperatures particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described in the prior art. These methods include providing the application of heat and pressure substantially concurrently by various means, including a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles generally takes place when the proper combination of heat, pressure and contact time is provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and they can be adjusted to suit particular machines, process conditions, and printing substrates.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate and/or belt members. The concurrent transfer of heat and the application of pressure in the nip affect the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus, increasing the background or interfering with the material being copied there. The so called “hot offset” occurs when the temperature of the toner is raised to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member.
The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface that has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser members to ensure that the toner is completely released from the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset. In addition to preventing hot offset, it is desirable to provide operational latitude as large as possible. By operational latitude it is intended to mean the difference in temperature between the minimum temperature required to fix the toner to the paper, the minimum fix temperature, and the temperature at which the hot toner will offset to the fuser roll, the hot offset temperature.
Generally, fuser and fixing rolls are prepared by applying one or more layers to a suitable substrate. For example, cylindrical fuser and fixer rolls are typically prepared by applying a fluoroelastomer layer, with or without additional layers, to an aluminum core. The coated roll is then heated in a convection oven to cure the fluoroelastomer material. Such processing is disclosed in, for example, U.S. Pat. Nos. 5,501,881, 5,512,409 and 5,729,813, the entire disclosures of which are incorporated herein by reference.
Surface layers of these types of members in an electrostatographic device thus typically have comprised silicone rubber or fluoroelastomers as a preferred material. For example, conventional materials known in the art as useful for intermediate transfer member surfaces include silicone rubbers, fluorocarbon elastomers such as are available under the trademark VITON™ from E.I. du Pont de Nemours & Co., polyvinyl fluoride such as available under the tradename TEDLAR™ also available from E.I. du Pont de Nemours & Co, various fluoropolymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA-TEFLON™), fluorinated ethylenepropylene copolymer (FEP), other TEFLON™-like materials, and the like and mixtures thereof.
U.S. Pat. No. 6,037,092, incorporated herein by reference in its entirety, discloses a fuser member comprising a substrate and at least one layer thereover, the layer comprising a crosslinked product of a liquid composition which comprises (a) a fluorosilicone, (b) a crosslinking agent, and (c) a thermal stabilizing agent comprising a reaction product of (i) a cyclic unsaturated-alkyl-group-substituted polyorganosiloxane, (ii) a linear unsaturated-alkyl-group-substituted polyorganosiloxane, and (iii) a metal acetylacetonate or metal oxalate compound.
U.S. Pat. No. 5,991,590, incorporated herein by reference in its entirety, describes a transfer member having a substrate, an outer silicone rubber layer, and a silicone polymer release agent material, wherein the release agent material is a polydimethyl siloxane cationic liquid emulsion.
U.S. Pat. No. 5,846,643 describes a fuser member for use in an electrostatographic printing machine has at least one layer of an elastomer composition comprising a silicone elastomer and a mica-type layered silicate, the silicone elastomer and mica-type layered silicate forming a delaminated nanocomposite with silicone elastomer inserted among the delaminated layers of the mica-type layered silicate.
U.S. Pat. No. 6,007,918 describes a fusing belt employing a polyimide substrate comprising a block copolymer derived from hexafluoroisopylidene-2,2′-bisphthalic anhydride 5-amino-(4-aminophenyl)-1,1,3-trimethylindane, and aminopropyl terminated polydimethylsiloxane.
U.S. Pat. No. 5,864,740 discloses a thermally stabilized silicone liquid composition and a toner fusing system using the thermally stabilized silicone liquid as a release agent, wherein the thermally stabilized silicone liquid contains a silicone liquid and a thermal stabilizer composition (including a reaction product from at least a polyorganosiloxane and a platinum metal compound (Group VIII compound) such as a ruthenium compound, excluding platinum).
U.S. Pat. No. 4,150,181 discloses a contact fuser assembly and method for preventing toner offset on a heated fuser member in an electrostatic reproducing apparatus which includes a base member coated with a solid, abrasion resistant material such as polyimide, poly(amide-imides), poly(imide-esters), polysulfones, and aromatic polyamides. The fuser member is coated with a thin layer of polysiloxane fluid containing low molecular weight fluorocarbon. Toner offset on the heated fuser member is prevented by applying the polysiloxane fluid containing fluorocarbon to the solid, abrasion resistant surface of the fuser member.
U.S. Pat. No. 4,711,818 discloses a thermally conductive dry release member and fusing method for use in electrostatic reproducing machines without the application of a release agent. The fuser member comprises a base support member and a thin deformable layer of a composition coated thereon, the composition comprising the crosslinked product of a mixture of at least one addition curable vinyl terminated or vinyl pendant polyfluoroorganosiloxane, filler, heat stabilizer, a crosslinking agent, and a crosslinking catalyst.
U.S. Pat. Nos. 5,464,703 and 5,563,202 disclose a fuser member useful for heat fixing an electrographic toner to a substrate, a composition of matter, and its preparation method. The fuser member has a core and a base cushion layer overlying the core. The base cushion layer includes a crosslinked poly(dimethylsiloxane-fluoroalkylsiloxane) elastomer that has tin oxide particles dispersed therein in a concentration of from 20 to 40 percent of the total volume of the base cushion layer.
An alternative process to conventional electrostatographic imaging is the recently developed process of ballistic aerosol marking. Ballistic aerosol marking is a process for applying a marking material to a substrate, directly or indirectly. In particular, the ballistic aerosol marking system includes a propellant that travels through a channel, and a marking material that is controllably (i.e., modifiable in use) introduced, or metered, into the channel such that energy from the propellant propels the marking material to the substrate. The propellant is usually a dry gas that can continuously flow through the channel while the marking apparatus is in an operative configuration (i.e., in a power-on or similar state ready to mark). Examples of suitable propellants include carbon dioxide gas, nitrogen gas, clean dry ambient air, gaseous products of a chemical reaction, or the like; preferably, non-toxic propellants are employed, although in certain embodiments, such as devices enclosed in a special chamber or the like, a broader range of propellants can be tolerated. The system is referred to as “ballistic aerosol marking” in the sense that marking is achieved by in essence launching a non-colloidal, solid or semi-solid particulate, or alternatively a liquid, marking material at a substrate. The shape of the channel can result in a collimated (or focused) flight of the propellant and marking material onto the substrate.
The propellant can be introduced at a propellant port into the channel to form a propellant stream. A marking material can then be introduced into the propellant stream from one or more marking material inlet ports. The propellant can enter the channel at a high velocity. Alternatively, the propellant can be introduced into the channel at a high pressure, and the channel can include a constriction (for example, de Laval or similar converging/diverging type nozzle) for converting the high pressure of the propellant to high velocity. In such a situation, the propellant is introduced at a port located at a proximal end of the channel (the converging region), and the marking material ports are provided near the distal end of the channel (at or further down-stream of the diverging region), allowing for introduction of marking material into the propellant stream.
In the situation where multiple ports are provided, each port can provide for a different color (for example, cyan, magenta, yellow, and black), pre-marking treatment material (such as a marking material adherent), post-marking treatment material (such as a substrate surface finish material, for example, matte or gloss coating, or the like), marking material not otherwise visible to the unaided eye (for example, magnetic particle-bearing material, ultraviolet-fluorescent material, or the like) or other marking material to be applied to the substrate. Examples of materials suitable for pre-marking treatment and post-marking treatment include polyester resins (either linear or branched); poly(styrenic) homopolymers; poly(acrylate) and poly(methacrylate) homopolymers and mixtures thereof; random copolymers of styrenic monomers with acrylate, methacrylate, or butadiene monomers and mixtures thereof; polyvinyl acetals; poly(vinyl alcohol)s; vinyl alcohol-vinyl acetal copolymers; polycarbonates; mixtures thereof; and the like. The marking material is imparted with kinetic energy from the propellant stream, and ejected from the channel at an exit orifice located at the distal end of the channel in a direction toward a substrate.
One or more such channels can be provided in a structure which, in one embodiment, is referred to herein as a printhead. The width of the exit (or ejection) orifice of a channel is typically on the order of about 250 microns or smaller, and preferably in the range of about 100 microns or smaller. When more than one channel is provided, the pitch, or spacing from edge to edge (or center to center) between adjacent channels can also be on the order of about 250 microns or smaller, and preferably in the range of about 100 microns or smaller. Alternatively, the channels can be staggered, allowing reduced edge-to-edge spacing. The exit orifice and/or some or all of each channel can have a circular, semicircular, oval, square, rectangular, triangular or other cross-sectional shape when viewed along the direction of flow of the propellant stream (the channel's longitudinal axis).
The marking material to be applied to the substrate can be transported to a port by one or more of a wide variety of ways, including simple gravity feed, hydrodynamic, electrostatic, ultrasonic transport, or the like. The material can be metered out of the port into the propellant stream also by one of a wide variety of ways, including control of the transport mechanism, or a separate system such as pressure balancing, electrostatics, acoustic energy, ink jet, or the like.
The marking material to be applied to the substrate can be a solid or semi-solid particulate material, such as a toner or variety of toners in different colors, a suspension of such a marking material in a carrier, a suspension of such a marking material in a carrier with a charge director, a phase change material, or the like. Preferably the marking material is particulate, solid or semi-solid, and dry or suspended in a liquid carrier. Such a marking material is referred to herein as a particulate marking material. A particulate marking material is to be distinguished from a liquid marking material, dissolved marking material, atomized marking material, or similar non-particulate material, which is generally referred to herein as a liquid marking material. However, ballistic aerosol marking processes are also able to utilize such a liquid marking material in certain applications.
Ballistic aerosol marking processes also enable marking on a wide variety of substrates, including direct marking on non-porous substrates such as polymers, plastics, metals, glass, treated and finished surfaces, and the like. The reduction in wicking and elimination of drying time also provides improved printing to porous substrates such as paper, textiles, ceramics, and the like. In addition, ballistic aerosol marking processes can be configured for indirect marking, such as marking to an intermediate transfer roller or belt, marking to a viscous binder film and nip transfer system, or the like.
The marking material to be deposited on a substrate can be subjected to post ejection modification, such as fusing or drying, overcoating, curing, or the like. In the case of fusing, the kinetic energy of the material to be deposited can itself be sufficient effectively to melt the marking material upon impact with the substrate and fuse it to the substrate. The substrate can be heated to enhance this process. Pressure rollers can be used to cold-fuse the marking material to the substrate. In-flight phase change (solid-liquid-solid) can alternatively be employed. A heated wire in the particle path is one way to accomplish the initial phase change. Alternatively, propellant temperature can accomplish this result. In one embodiment, a laser can be employed to heat and melt the particulate material in-flight to accomplish the initial phase change. The melting and fusing can also be electrostatically assisted (i.e., retaining the particulate material in a desired position to allow ample time for melting and fusing into a final desired position). The type of particulate can also dictate the post-ejection modification. For example, ultraviolet curable materials can be cured by application of ultraviolet radiation, either in flight or when located on the material-bearing substrate.
Since propellant can continuously flow through a channel, channel clogging from the build-up of material is reduced (the propellant effectively continuously cleans the channel). In addition, a closure can be provided that isolates the channels from the environment when the system is not in use. Alternatively, the printhead and substrate support (for example, a platen) can be brought into physical contact to affect a closure of the channel. Initial and terminal cleaning cycles can be designed into operation of the printing system to optimize the cleaning of the channel(s). Waste material cleaned from the system can be deposited in a cleaning station. It is also possible, however, to engage the closure against an orifice to redirect the propellant stream through the port and into the reservoir thereby to flush out the port.
Further details on the ballistic aerosol marking process are disclosed in, for example, U.S. Pat. Nos. 6,511,149, 6,416,157, 6,340,216, 6,523,928, 6,467,862, 6,290,342, 6,328,409, 6,454,384, 6,136,442, 6,416,156, 6,116,718, 6,265,050, 6,291,088, 6,309,042, and 6,302,513, and U.S. patent application Ser. No. 09/163,799, filed Sep. 30, 1998, the entire disclosures of which are incorporated herein by reference.
Silicone rubbers are widely used in fusing subsystems, in conventional electrostatographic imaging. However silicone rubbers employed on the surface of fuser rolls lack the wear resistance required of a digital color printer.
Accordingly, while known compositions and processes are suitable for their intended purposes, a need remains for improved materials with better wear resistance. Further, a need remains for a fuser, pressure, transfer and/or transfix member surface layer that does not result in significant surface degradation and loss of transfer properties of the outer layer of the member during operation